Light-harvesting complex structure

Despite considerable efforts very few membrane proteins have yielded crystals that diffract x-rays to high resolution. In fact, only about a dozen such proteins are currently known, among which are porins (which are outer membrane proteins from bacteria), the enzymes cytochrome c oxidase and prostaglandin synthase, and the light-harvesting complexes and photosynthetic reaction centers involved in photosynthesis. In contrast, many other membrane proteins have yielded small crystals that diffract poorly, or not at all, using conventional x-ray sources. However, using the most advanced synchrotron sources (see Chapter 18) it is now possible to determine x-ray structures from protein crystals as small as 20 pm wide which will permit more membrane protein structures to be elucidated. 

Koepke, J., et al. The crystal structure of the light-harvesting complex II (B800-850) from Rhodospirillum molis-chianum. Structure 4 581-597, 1996. 

McDermott, G., S. Prince, A. Freer et al. 1995. Crystal structure of an integral membrane light-harvesting complex from photosynthetic bacteria. Nature 374 517-521. 

A short, intermediate-level review of the structure and function of the light-harvesting complex of the purple bacteria and exci-ton flow to the reaction center. 

Figure 23-29 (A) Stereoscopic drawing of light-harvesting complex from the dinoflagellate protozoan Amphidinium carterae. The central cavity contains eight molecules of peridinin, two of which can be seen protruding from the top. Deeply buried toward the bottom are two molecules of Chi a. Also present are two molecules of digalactosyl diacylglycerol. From Hofmann et al.268 Courtesy of Wolfram Welte. (B) Structure of peridinin.

Figure 11.7 Structures and absorption spectra of chlorophylls a and b schematic view of light harvesting complex. (Data from Protein Data Bank (DO 10.2210/pdb2BHW/pdb))...

Fig. 5. Specific structural elements (amino acid residues boxed) of antenna polypeptides of B880 (A), B800-850 (B) and B800-820 (C) light-harvesting complexes from purple bacteria.

G. McDermott, S.M. Prince, A.A. Freer, A.M. Hawthornthwaite-Lawless, M.Z. Pa-piz, R.J. Cogdell, N.W. Isaacs, Crystal-Structure of an Integral Membrane Light-Harvesting Complex from Photosynthetic Bacteria , Nature, 374,517 (1995)... 

J. Koepke, X.C. Hu, C. Muenke, K. Schulten, H. Michel H, The Crystal Structure of the Light-Harvesting Complex II (B800-850) from Rhodospirillum Molischianum , Structure, 4, 581 (1996)... 

Prince SM, Howard TD, Myles DA, Wilkinson C, Papiz MZ, Freer AA, Cogdell RJ, Isaacs NW. Detergent structure in crystals of the integral membrane light-harvesting complex LH2 from Rhodopseudomonas acidophila strain 10050. J. Mol. Biol. 2003 326 307-315. 

---